Sometimes it is useful for the SD driver to know the type of card that is in
use so that dynamic sd bus clocking can be enabled or disabled.
Dynamic clocks are a feature of sd 3.0 and we can support this in our v2.0
controller.
The problem is that some SDIO cards are not happy when the clocks are
dynamically stopped. I have not seen any issues with SD/mmc/eMMC cards. I
suspect the reason for the SDIO problems is that the cards need the clock since
SDIO cards can interrupt the CPU for service and the other card types cannot.
The information about the type of card being used is known by the mmc layer
when
mmc_alloc_card(struct mmc_host *host, struct device_type *type) --- core/bus.c
is called but the sd driver cannot get to this information when set_ios() is
called by the mmc layer since the host->card field is filled in too late.
I have added host->card = card to
struct mmc_card *mmc_alloc_card(struct mmc_host *host, struct device_type *type)
{
struct mmc_card *card;
card = kzalloc(sizeof(struct mmc_card), GFP_KERNEL);
if (!card)
return ERR_PTR(-ENOMEM);
card->host = host;
device_initialize(&card->dev);
card->dev.parent = mmc_classdev(host);
card->dev.bus = &mmc_bus_type;
card->dev.release = mmc_release_card;
card->dev.type = type;
+ host->card = card;
return card;
}
and this works for me provided the sd driver remembers to check for card being
NULL in the driver specific set_clock code.
My pseudo code is
if (host->mmc->card == NULL)
dynamic_clocks=FALSE;
else if host->mmc->card == MMC_TYPE_SDIO)
dynamic_clocks = TRUE;
else
dynamic_clocks = FALSE;
My question is: Is there a better way to pass the type of card to the sd
driver?
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